1. Field of the Invention
The present invention relates to an electrical switching apparatus operating mechanism and, more specifically to an interlock assembly that prevents the actuation of the latch assembly in configurations wherein the closing assembly should not be actuated.
2. Background Information
An electrical switching apparatus, typically, includes a housing, at least one bus assembly having a pair of contacts, a trip device, and an operating mechanism. The housing assembly is structured to insulate and enclose the other components. The at least one pair of contacts include a fixed contact and a movable contact and typically include multiple pairs of fixed and movable contacts. Each contact is coupled to, and in electrical communication with, a conductive bus that is further coupled to, and in electrical communication with, a line or a load. A trip device is structured to detect an over current condition and to actuate the operating mechanism. An operating mechanism is structured to both open the contacts, either manually or following actuation by the trip device, and close the contacts.
That is, the operating mechanism includes both a closing assembly and an opening assembly, which may have common elements, that are structured to move the movable contact between a first, open position, wherein the contacts are separated, and a second, closed position, wherein the contacts are coupled and in electrical communication. The operating mechanism includes a rotatable pole shaft that is coupled to the movable contact and structured to move each movable contact between the closed position and the open position. Elements of both the closing assembly and the opening assembly are coupled to the pole shaft so as to effect the closing and opening of the contacts. The closing assembly may be actuated manually by a user input or in response to an input from a remote actuator.
The trip device included an over-current sensor, a latch assembly and may have included one or more additional links that were coupled to the toggle assembly. Alternately, the latch assembly was directly coupled to the toggle assembly. When an over-current situation occurred, the latch assembly was released allowing the opening spring to cause the toggle assembly to collapse. When the toggle assembly collapsed, a closing spring coupled to the pole shaft caused the pole shaft to rotate and thereby move the movable contacts into the open position.
Low and medium voltage electrical switching apparatus typically had stored energy devices, such as a closing spring and an opening spring, and at least one link coupled to the pole shaft. The at least one link, typically, included two links that acted cooperatively as a toggle assembly and which were coupled to each other at a toggle joint. When the contacts were open, the toggle assembly was in a first, collapsed configuration and, conversely, when the contacts were closed, the toggle assembly was, typically, in a second, toggle position, that is, an in-line configuration, or in a slightly over-toggle position. The closing spring was usually compressed, or “charged,” by a motor or a user utilizing a lever arm. The closing spring, typically, holds more stored energy than the opening springs and during the closing operation wherein the contacts are moved to the second, closed position, the opening spring was charged. The opening spring biased the pole shaft, and therefore the toggle assembly, to the collapsed position. The opening spring and toggle assembly were maintained in the second, toggle position by the trip device.
Typically, the closing spring is recharged immediately after a closing procedure was completed. Thus, the closing assembly was set to be actuated in the event the contacts were opened, e.g. upon a trip. The closing assembly was typically actuated by a remote device or by an “on” button disposed on the face of the electrical switching apparatus. The remote device and/or the on button is coupled to a closing assembly latch, which typically included a D-shaft against which a latch member was biased by force from the closing springs. Actuation of the closing assembly caused the D-shaft to rotate and allowed the latch member to rotate thereby releasing the closing springs.
However, having the closing spring in a charged state could also result in damage to the operating mechanism if the closing spring was released too often while the contacts were closed. That is, if the closing spring was released by a user pressing the on button when the contacts were closed, energy from the spring would cause the various components of the closing assembly to, possibly, impact upon each other without the benefit of the energy being dissipated to the opening springs or contact springs or other such components. Furthermore, if the closing spring was inappropriately released when the contacts were closed, then electrical switching apparatus tripped and then called on to immediately re-close, a non-charged closing spring could result in a delay of service. There are other circumstances wherein the closing assembly should not be activated. For example, immediately after a closing procedure the closing spring should be fully recharged and latched prior to releasing the closing spring again. However, if a user were to hold the on button during the recharging procedure, the closing spring could not be latched and, as soon as the charging operation was completed, the closing spring would discharge. That is, there should be only one attempt to release the closing springs per application of the on button and that attempt should only occur when the closing springs are charged and permitted to close. For example, the closing spring should not be permitted to close when the trip device is used to keep the contacts in the open state. For example, when an electrical switching apparatus is being worked upon, a safety interlock typically holds the trip device in a tripped configuration, thereby ensuring the contacts are in the first open position. Generally, in such a situation, the contacts should not be closed by the closing assembly and the closing springs should not be allowed to discharged. Thus, generally, any time the contacts are closed, or when the contacts should be kept open, a close command by the closing assembly should not be allowed to close the contacts.
To prevent accidental closure of the contacts in these situations, electrical switching apparatuses included an interlock. The interlock was structured to decouple the on button, or a remote actuator, from the latch assembly D-shaft. Once the actuation device was decoupled from the latch assembly D-shaft, pressing the on button or actuating the remote actuator had no effect on the latch assembly D-shaft. The interlock typically relied upon a link structured to pivot and to slide. That is, the link included an elongated slot through which a pivot pin extended. This allowed the link to move with two degrees of freedom, i.e., (1) pivoting and (2) sliding.
Such an interlock would operate, generally, in the following manner. With the pivot pin at one end of the slot, the link was disposed adjacent to the D-shaft. When the actuator, that is the on button or the remote actuator, was actuated, the link would pivot to operatively engage the D-shaft and cause the D-shaft to rotate thereby releasing the latch and the closing spring. When the closing assembly should not have been allowed to close the contacts, the interlock moved the link so that the pivot pin was disposed at the other end of the slot. This motion spaced the link from the D-shaft and/or the actuator. Thus, when the on button or the remote actuator was actuated, the subsequent pivoting motion of the link did not cause the link to engage the D-shaft/actuator as the link was now spaced from the D-shaft/actuator. As such, the interlock prevented the contact from being closed as a result of actuating the on button or the remote actuator. It is noted that the interlock could also be structured so that the sliding motion actuated the D-shaft and the pivoting motion separated the link from the D-shaft.